Method of singulating semiconductor wafer having back layer

ABSTRACT

In one embodiment, die are singulated from a wafer having a back layer by placing the wafer onto a first carrier substrate with the back layer adjacent the carrier substrate, forming singulation lines through the wafer to expose the back layer within the singulation lines, and using a mechanical device to apply localized pressure to the wafer to separate the back layer in the singulation lines. The localized pressure can be applied through the first carrier substrate proximate to the back layer, or can be applied through a second carrier substrate attached to a front side of the wafer opposite to the back layer.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. application Ser.No. 14/057,756 filed on Oct. 18, 2013 and issued as U.S. Pat. No.9,136,173 on Sep. 15, 2015, which claims the benefit of priority from:U.S. Provisional Application No. 61/723,548, which was filed on Nov. 7,2012, from U.S. Provisional Application No. 61/750,520, which was filedon Jan. 9, 2013, and from U.S. Provisional Application No. 61/774,081,which was filed on Mar. 7, 2013, all of which are fully incorporated byreference herein.

BACKGROUND

The present invention relates, in general, to electronics and, moreparticularly, to methods and apparatus for forming semiconductors.

In the past, the semiconductor industry utilized various methods andequipment to singulate individual semiconductor die from a semiconductorwafer on which the die was manufactured. Typically, a technique calledscribing or dicing was used to either partially or fully cut through thewafer with a diamond cutting wheel along scribe grids or singulationlines that were formed on the wafer between the individual die. To allowfor the alignment and the width of the dicing wheel each scribe gridusually had a large width, generally about one hundred fifty (150)microns, which consumed a large portion of the semiconductor wafer.Additionally, the time required to scribe each singulation line on thesemiconductor wafer could take over one hour or more. This time reducedthe throughput and manufacturing capacity of a production facility.

Other methods, which have included thermal laser separation (TLS), laserablation dicing, and plasma dicing, have been explored as alternativesto scribing. Plasma dicing is a promising process compared to scribingand other alternative processes because it supports narrower scribelines, has increased throughput, and can singulate die in varied andflexible patterns. However, plasma dicing has had manufacturingimplementation challenges. Such challenges have includednon-compatibility with wafer backside layers, such as back metal layers,because the etch process has been unable to effectively remove orseparate the backside layers from the singulation lines. Removing orseparating the backside layers from the scribe lines is necessary tofacilitate subsequent processing, such as pick-and-place and assemblyprocesses.

Accordingly, it is desirable to have a method of singulating die from asemiconductor wafer that removes or separates the backside layers fromwithin the singulation lines. It would be beneficial for the method tobe cost effective and to minimize any damage to or contamination of theseparated die.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a reduced plan view of an embodiment of a wafer inaccordance with the present invention;

FIGS. 2-5 illustrate partial cross-sectional views of an embodiment of athe wafer of FIG. 1 at various stages in a process of singulating diefrom the wafer in accordance with an embodiment of the presentinvention;

FIG. 6 illustrates a cross-sectional view of the wafer of FIG. 1 at astage of processing within an apparatus in accordance with anotherembodiment of the present invention;

FIG. 7 illustrates a partial cross-sectional view of an embodiment ofthe wafer of FIG. 5 or FIG. 6 at a later stage of processing inaccordance with an embodiment of the present invention;

FIG. 8 illustrates a cross-sectional view of a wafer in accordance witha second embodiment of the present invention;

FIG. 9 illustrates a top view of the second embodiment after subsequentprocessing in accordance with the present invention;

FIG. 10 illustrates a cross-sectional view of the second embodimentafter subsequent processing in accordance with the present invention;

FIG. 11 illustrates a cross-sectional view of the second embodimentafter additional processing in accordance with the present invention;

FIG. 12 illustrates a cross-sectional view of the second embodimentafter further processing in accordance with the present invention;

FIG. 13 illustrates a cross-sectional view of the second embodiment at alater stage of fabrication in accordance with the present invention;

FIG. 14 illustrates a cross-sectional view of the second embodiment inaccordance with an alternative manufacturing process;

FIG. 15 illustrates the wafer of FIG. 10 in accordance with anadditional embodiment of the present invention;

FIG. 16 illustrates a cross-sectional view of the additional embodimentafter further processing in accordance with the present invention;

FIG. 17 illustrates a cross-sectional view of the additional embodimentat a later stage of fabrication in accordance with the presentinvention; and

FIG. 18 illustrates a flowchart of a process for singulating back layermaterial in accordance with a further embodiment of the presentinvention.

For simplicity and clarity of the illustration, elements in the figuresare not necessarily drawn to scale, and the same reference numbers indifferent figures denote the same elements. Additionally, descriptionsand details of well-known steps and elements are omitted for simplicityof the description. For clarity of the drawings, certain regions ofdevice structures, such as doped regions or dielectric regions, may beillustrated as having generally straight line edges and precise angularcorners. However, those skilled in the art understand that, due to thediffusion and activation of dopants or formation of layers, the edges ofsuch regions generally may not be straight lines and that the cornersmay not be precise angles. Furthermore, the term “major surface” whenused in conjunction with a semiconductor region, wafer, or substratemeans the surface of the semiconductor region, wafer, or substrate thatforms an interface with another material, such as a dielectric, aninsulator, a conductor, or a polycrystalline semiconductor. The majorsurface can have a topography that changes in the x, y and z directions.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a reduced plan view that graphically illustrates a wafer 10 ata later step in fabrication. In one embodiment, wafer 10 can be asemiconductor substrate. Wafer 10 includes a plurality of semiconductordie, such as die 12, 14, 16, and 18, that are formed on or as part ofsemiconductor wafer 10. Die 12, 14, 16, and 18 are spaced apart fromeach other on wafer 10 by spaces in which singulation lines are to beformed or defined, such as scribe lines or singulation lines 13, 15, 17,and 19. As is well known in the art, all of the semiconductor die onwafer 10 generally are separated from each other on all sides by areaswhere scribe lines or singulation lines, such as singulation lines 13,15, 17, and 19 are to be formed. Die 12, 14, 16, and 18 can be any kindof electronic device including semiconductor devices such as, diodes,transistors, discrete devices, sensor devices, optical devices,integrated circuits or other devices known to one of ordinary skill inthe art. In one embodiment, wafer 10 has completed wafer processingincluding the formation of a backside layer described hereinafter.

FIG. 2 illustrates an enlarged cross-sectional view of wafer 10 at anearly step in a die singulation method in accordance with a firstembodiment. In one embodiment, wafer 10 is attached to a carriersubstrate, transfer tape, or carrier tape 30 that facilitates supportingthe plurality of die after they are singulated. Such carrier tapes arewell known to those of skill in the art. In one embodiment, carrier tape30 can be attached to a frame 40, which can include frame portions orportions 401 and 402. As illustrated, carrier tape 30 can be attached tosurface 4010 of frame portion 401 and to surface 4020 of frame portion402.

In the cross-section illustrated, wafer 10 can include a bulk substrate11, such as a silicon substrate, which can include opposing majorsurfaces 21 and 22. In other embodiments, bulk substrate 11 can compriseother semiconductor materials such as heterojunction semiconductormaterials. In one embodiment, contact pads 24 can be formed along, in,on, or above portions of major surface 21 to provide for electricalcontact between structures formed within substrate 11 and next levels ofassembly or external elements. For example, contact pads 24 can beformed to receive bonding wires or clips that may be subsequently beattached to contact pads 24, or contact pads 24 can be formed to receivea solder ball, bump or other type of attachment structure. Contact pads24 generally can be a metal or other conductive material. Typically, adielectric material 26 such as, a blanket deposited dielectric layer canbe formed on or overlying major surface 21 to function as a passivationlayer for wafer 10. In one embodiment, dielectric material 26 can be amaterial that etches at a slower rate than that of substrate 11. In oneembodiment, dielectric material 26 can be a silicon oxide, siliconnitride, or polyimide when substrate 11 is silicon.

In one embodiment, openings can be formed in dielectric material 26 (andother dielectric layers that can be formed underneath dielectricmaterial 26) to expose underlying surfaces of contact pads 24 andsurfaces of substrate 11 where singulation lines 13, 15, 17, and 19 areto be formed. In one embodiment, a patterned photoresist layer can beused for the openings using an etching process. As illustrated in FIG. 2and in accordance with the present embodiment, wafer 10 further includesa layer of material 28 formed on or overlying major surface 22 of wafer10. In one embodiment, layer 28 can be a conductive back metal layer. Inone embodiment, layer 28 can be a multi-layer metal system such as,titanium/nickel/silver, titanium/nickel/silver/tungsten,chrome/nickel/gold, copper, copper alloys, gold, or other materialsknown to those skilled in the art. In another embodiment, layer 28 canbe a wafer backside coating (WBC) film, such as a die-attach coating orfilm. In one embodiment, layer 28 can be formed having or provided withgaps, spaces, or channels between at least some adjacent die. In afurther embodiment, the gaps are substantially aligned withcorresponding spaces on the opposite side of wafer 10 where singulationlines 13, 15, 17, 19 will be formed. In another embodiment, layer 28 isseparated from edges of least some of the die.

FIG. 3 illustrates an enlarged cross-sectional view of wafer 10 at asubsequent step during a singulation process. In FIG. 3, a plasma or dryetch singulation process is illustrated. It is understood that othersingulation processes can be used. In one embodiment, wafer 10 can bemounted on carrier tape or film 30 and then can be placed within an etchapparatus 300, such as a plasma etch apparatus. In one embodiment,substrate 11 can be etched through the openings to form or definesingulation lines or openings 13, 15, 17, and 19 extending from majorsurface 21. The etching process can be performed using a chemistry(generally represented as arrows 31) that selectively etches silicon ata much higher rate than that of dielectrics and/or metals. In oneembodiment, wafer 10 can be etched using a process commonly referred toas the Bosch process. In one embodiment, wafer 10 can be etched usingthe Bosch process in a deep reactive ion etch system. In one embodiment,the width of singulation lines 13, 15, 17, and 19 can be from about fivemicrons to about twenty microns. Such a width is sufficient to ensurethat the openings that form singulation lines 13, 15, 17, and 19 can beformed completely through substrate 11 stopping proximate to or on layer28 because of the etch selectivity as generally illustrated in FIG. 4.In one embodiment, layer 28 can be used as a stop layer for the plasmaetch singulation process. In one embodiment, singulation lines 13, 15,17, and 19 can be formed in about five to about thirty minutes using theBosch process.

FIG. 5 illustrates a cross-sectional view of wafer 10 at a subsequentprocess step. In one embodiment, frame 40 can be placed onto a holdingdevice 63 or support structure 63. In one embodiment, support structure63 can include pedestal(s) or standoff(s) 631 that is configured toprovide a gap 632, depression 632, or well 632 or another structure thatallows wafer 10 and tape 30 to expand without contacting supportstructure 63 during subsequent processing. In one embodiment, frame 40can be reversibly attached to support structure 63 using vacuum or aclamping structure.

In one embodiment, layer 28 is separated by a mechanical device 61, suchas a stylus 610 or a rotating wheel 620 as illustrated in FIG. 5. In oneembodiment, surface 21 is free floating (i.e., well 632 is an air gap)as illustrated in FIG. 5. In another embodiment, surface 21 can be incontact with a flexible support structure such as polyimide or anynumber of flexible polymers. In one embodiment, mechanical device 61 isconfigured to provide a reduced area or localized pressure point 623onto wafer 10. In one embodiment, mechanical device 61 can be configuredto have a radius that is approximately half the width of die 12, 14, 16,and 19. In another embodiment, mechanical device 61 can be configured tohave a radius that is approximately equal to a width of die 12, 14, 16,and 19. In one embodiment, the radius of mechanical device 61 can beselected to be approximately double the size of die 12, 14, 16, and 19or greater. Mechanical device 61 can be configured with pressure, speed,and alignment control. Also, mechanical device 61 can be configured witha quick disconnect device 611 to allow for simplified removal ofmechanical device 61 from a main apparatus, which improves processflexibility. Mechanical device 61 can be made of a metal, rubber,organic solid material (for example, a plastic), ceramic, compositematerial, combinations thereof, or other materials known to those ofordinary skill in the art. In the embodiment illustrated, rotating wheel620 can be passed along tape 30 with sufficient pressure applied toseparate layer 28 while minimizing any detrimental effects to die 12,14, 16, and 19. In one embodiment, more than one mechanical device 61can be used to separate layer 28.

FIG. 6 illustrates a cross-sectional view of wafer 10 at subsequentprocess step as an alternative embodiment to FIG. 5. In one embodiment,multiple mechanical devices 71 can be formed on a plate structure 710.Mechanical devices 71 can be similar to mechanical devices 61. In oneembodiment, mechanical devices 71 can be styluses configured to providelocalized pressure points onto wafer 10. In one embodiment, platestructure 710 can be placed against tape 30 with sufficient pressureapplied to separate layer 28. In one embodiment, plate structure 710 canrotate as illustrated by arrow 712. In another embodiment, frame 40 canbe rotated over plate structure 710 as illustrated by arrow 714 or movedhorizontally back-and-forth over plate structure 710 as illustrated byarrows 716 and 718 to separate layer 28. In a subsequent step, die 12,14, 16, and 18 can be removed from carrier tape 30 as part of a furtherassembly process using, for example, a pick-and-place apparatus 81 asgenerally illustrated in FIG. 7. In one embodiment, carrier tape 30 canbe exposed to a UV light source prior to the pick-and-place step toreduce the adhesiveness of the tape.

FIG. 8 illustrates a partial cross-sectional view of a wafer 100 inaccordance with a second embodiment. In one embodiment, substrate 100can be a semiconductor wafer similar to semiconductor wafer 10, and canhave a plurality of die or semiconductor die 12, 14, 16, and 18. Die 12,14, 16, and 18 are spaced apart from each other on substrate 100 byspaces in which singulation lines are to be formed or defined, such asscribe lines or singulation lines 13, 15, 17, and 19. Die 12, 14, 16,and 18 can be any kind of electronic device including semiconductordevices such as, diodes, transistors, discrete devices, sensor devices,optical devices, integrated circuits or other devices known to one ofordinary skill in the art.

In one embodiment, wafer 100 has completed wafer processing includingthe formation of a backside layer 281. In one embodiment, backside layer281 is a continuous film. The method in accordance with the presentembodiment is configured for processing wafers having thicker layers ormaterials on the backside of wafer 100. It was found in some wafers withthicker backside materials that the cracks that form during theseparation process can undesirably propagate or wander into the activeareas of the die, which can lead to device failures. In one embodiment,layer 281 can be a wafer backside coating or WBC formed using, forexample stencil, screen printing, and/or spin coating techniques. By wayof example, the WBC can be a die attach adhesive material having athickness from about 5 microns to about 50 microns. In one embodiment,the WBC can be a die attach adhesive material having a thickness ofabout 20 microns. Layer 281 can be configured to facilitate theattachment of die 12, 14, 16, and 18 to a next level of assembly, suchas a leadframe or a printed circuit board. In another embodiment, layer281 can be a back metal layer having a thickness greater than about 2microns or 3 microns. In one embodiment, layer 281 can be atitanium/nickel/gold/tin (Ti/Ni/Au/Sn) back metal structure having athickness greater than about 3 microns. As those skilled in the artappreciate, whether the present embodiment is used can depend on notonly thickness of the materials present, but also the kinds materialspresent. In one embodiment, layer 281 can be formed having or providedwith gaps, spaces, or channels between at least some adjacent die. In afurther embodiment, the gaps are substantially aligned withcorresponding spaces on the opposite side of wafer 10 where singulationlines 13, 15, 17, 19 will be formed. In another embodiment, layer 281 isseparated from edges of least some of the die.

FIG. 9 illustrates a top view of wafer 100 after subsequent processingin which singulation lines or openings 13, 15, 17, and 19 are formed. Inone embodiment, wafer 100 can be mounted on carrier tape 30 with layer281 against carrier tape 30. In one embodiment, carrier tape 30 ismounted to frame 40. Wafer 100 can then be placed into the etchapparatus as described in FIG. 3 to form or define singulation lines 13,15, 17, and 19. FIG. 10 illustrates a cross-sectional view of wafer 100after singulation lines 13, 15, 17 and 19 are defined. In oneembodiment, singulation lines 13, 15, 17 and 19 end or terminateadjacent or proximate to or stop on layer 281.

FIG. 11 illustrates a cross-sectional view of wafer 100 after additionalprocessing. In one embodiment, a carrier film or substrate 310 is placedoverlying the front surface or the surface opposite to layer 281. In oneembodiment, carrier film 310 can be a carrier tape with characteristicssimilar to carrier tape 30, a carrier tape with lighter adhesivecompared to carrier tape 30, a protective film, or other materials asknown to those of ordinary skill in the art. In one embodiment, carrierfilm 310 overlaps onto carrier 40 as illustrated in FIG. 11. Carriertape 30 can be removed to expose layer 281. In an optional step, amechanical tool 365, such as a scribe can be used to form scribe lines267, which are generally aligned with singulation lines 13, 15, 17, and19.

FIG. 12 illustrates a cross-sectional view of wafer 100 at a subsequentprocess step. In one embodiment, frame 40 can be placed onto a holdingdevice 63 or support structure 63. In one embodiment, support structure63 can include pedestal(s) or standoff(s) 631 that is configured toprovide a gap 632, depression 632, or well 632 or another structure thatallows wafer 100 and film 310 to expand without contacting supportstructure 63 during subsequent processing. In one embodiment, frame 40can be reversibly attached to support structure 63 using vacuum or aclamping structure.

In one embodiment, layer 281 is separated by a mechanical device 61,such as a stylus 610 or a rotating wheel 620 as illustrated in FIG. 12.In one embodiment, layer 281 is free floating as illustrated in FIG. 12.In another embodiment, surface 281 can be in contact with a flexiblesupport structure such as polyimide or any number of flexible polymers.In one embodiment, mechanical device 61 is configured to provide areduced area or localized pressure point 623 onto wafer 10. In oneembodiment, mechanical device 61 can be configured to have a radius thatis approximately half the width of die 12, 14, 16, and 19. In anotherembodiment, mechanical device 61 can be configured to have a radius thatis approximately equal to a width of die 12, 14, 16, and 19. In oneembodiment, the radius of mechanical device 61 can be selected to beapproximately double the size of die 12, 14, 16, and 19. Mechanicaldevice 61 can be configured with pressure, speed, and alignment control.Also, mechanical device 61 can be configured with a quick disconnectdevice 611 to allow for simplified removal of mechanical device 61 froma main apparatus, which improves process flexibility. Mechanical device61 can be made of a metal, rubber, organic solid material (for example,a plastic), ceramic, composite material, or combinations thereof. In theembodiment illustrated, rotating wheel 620 can be passed along tape 301with sufficient pressure applied to separate layer 281 while minimizingany detrimental effects to die 12, 14, 16, and 19. In one embodiment,more than one mechanical device 61 can be used to separate layer 281.

FIG. 13 illustrates a cross-sectional view of wafer 100 at a subsequentfabrication step. In one embodiment, a carrier tape 320 is placed on theback surface or the surface adjacent layer 281 and carrier film 310 canbe removed from the opposite side. In one embodiment, carrier tape 320overlaps onto frame 40. In one embodiment, frame 40 with carrier tape320 and wafer 100 can be placed within a mechanical device that helpsspread-out or expand carrier tape 320 to better facilitate, for example,a pick and place step. In one embodiment, frame 40 can be placed betweenclamp portions 816 and 818 as generally illustrated in FIG. 13. In oneembodiment, step or stand-off portions 821 can be placed or attachedonto clamp portions 818 to provide a structure for expanding orstretching carrier tape 320. This expansion effect can increase thedistance between adjacent die on wafer 100 to better facilitate theremoval of the individual die from carrier tape 320. In one embodiment,carrier tape 320 can be exposed to UV light to reduce the adhesivecharacteristics of the tape to make removal of the die easier.

FIG. 14 illustrates a cross-sectional and perspective view of wafer 100at subsequent process step as an alternative embodiment to FIG. 12. Inone embodiment, multiple mechanical devices 71 can be formed on a platestructure 710. Mechanical devices 71 can be similar to mechanicaldevices 61. In one embodiment, mechanical devices 71 can be stylusesconfigured to provide localized pressure points onto wafer 100. In oneembodiment, plate structure 710 can be placed against film 310 withsufficient pressure applied to separate layer 281. In one embodiment,plate structure 710 can rotate as illustrated by arrow 712. In anotherembodiment, frame 40 can be rotated over plate structure 710 asillustrated by arrow 714 or moved horizontally back-and-forth over platestructure 710 as illustrated by arrows 716 and 718 to separate layer281. In a subsequent step, die 12, 14, 16, and 18 can be removed fromthe carrier tape as part of a further assembly process using, forexample, the method described and generally illustrated in FIG. 13. Inone embodiment, the carrier tape can be exposed to a UV light sourceprior to the pick-and-place step to reduce the adhesiveness of the tape.It is understood that prior to pick and place an additional carrier tapecan be placed adjacent layer 281 and carrier film 310 can be removed.

FIG. 15 illustrates a cross-sectional view of wafer 100 as analternative embodiment after processing described in conjunction withFIG. 10. In one embodiment, carrier film 310 is placed overlying thefront surface or the surface opposite to layer 281. In one embodiment,carrier film 310 overlaps onto carrier 40 as illustrated in FIG. 15. Inthe present embodiment, carrier tape 30 is left in place for additionalprocessing. It should be noted that FIG. 15 represents an idealizedimage and that carrier film 310 and carrier tape 30 may come intocontact with each other; optionally an additional release layer (notshown) may be added between carrier film 310 and carrier tape 30.

FIG. 16 illustrates a cross-sectional view of wafer 100 at a subsequentprocess step. In one embodiment, frame 40 can be placed onto a holdingdevice 731 or support structure 731. In one embodiment, supportstructure 731 can be configured to include a gap 732, depression 732, orwell 732 or another structure that allows wafer 100 and tape 30 toexpand without contacting support structure 731 during subsequentprocessing. Support structure 731 may be heated or cooled to heat orcool layer 30. Support structure 731 may have adjustable vacuum or airpressure against layer 30. In one embodiment, frame 40 can be reversiblyattached to support structure 731 using vacuum or a clamping structure.In an optional embodiment, a compressive layer 733 can be placed withinwell 732 to provide additional elastic, resistive, or reactive forceduring the singulation of layer 281. In one embodiment, compressivelayer 733 can be a rubber pad or a pressurized membrane structure.

In one embodiment, layer 281 is separated by mechanical device 81, suchas a stylus 810 as illustrated in FIG. 16, which is applied to the frontside of wafer 100 through film 310. In accordance with the presentembodiment, the singulation of layer 281 is carried with wafer 100placed between tape 30 and film 310. Mechanical device 81 is configuredto provide a mechanical force along the front side of wafer 100sufficient to propagate separation lines or cracks within singulationlines 13, 15, 17, and 19. In one embodiment, mechanical device 81 isconfigured to provide a reduced area or localized pressure point 823onto wafer 100. In one embodiment, stylus 810 can be configured to havea radius that is approximately half the width of die 12, 14, 16, and 18.In another embodiment, stylus 810 can be configured to have a radiusthat is approximately equal to a width of die 12, 14, 16, and 18. In oneembodiment, the radius of stylus 810 can be selected to be approximatelydouble the size or greater of die 12, 14, 16, and 18. Mechanical device81 can be configured with pressure, speed, and alignment control. Also,mechanical device 81 can be configured with a quick disconnect device811 to allow for simplified removal of mechanical device 81 from a mainapparatus, which improves process flexibility. Mechanical device 81 canbe made of a metal, rubber, organic solid material (for example, aplastic), ceramic, composite material, combinations thereof, or othermaterials as known to those of ordinary skill in the art. In oneembodiment, more than one mechanical device 81 can be used to separatelayer 281.

FIG. 17 illustrates a cross-sectional view of wafer 100 at a subsequentfabrication step. In one embodiment, carrier film 310 can be removedfrom the front side of wafer 100 leaving carrier tape 30 in place. Inone embodiment, frame 40 with carrier tape 30 and wafer 100 can beplaced into a mechanical device that helps spread-out or expand carriertape 30 to better facilitate, for example a pick and place step. In oneembodiment, frame 40 can be placed between clamp portions 816 and 818 asgenerally illustrated in FIG. 17. In one embodiment, step or stand-offportions 821 can be placed or attached onto clamp portions 818 toprovide a structure for expanding or stretching carrier tape 320. Thisexpansion effect can increase the distance between adjacent die on wafer100 to better facilitate the removal of the individual die from carriertape 30. In one embodiment, carrier tape 30 can be exposed to UV lightto reduce the adhesive characteristics of the tape to make removal ofthe die easier.

FIG. 18 illustrates a flow chart for singulating thick backside materialin accordance with another embodiment. FIG. 18 will be described usingwafer 100 embodiment starting at FIG. 10 after wafer 100 has beensingulated. It is understood that such singulation can be by any methodwhere the singulation terminates proximate to backside layer 281. Instep 1300 carrier film 310 is applied or attached to the front side ofwafer 100 with carrier tape 30 adjacent to layer 281. In the presentembodiment, carrier film 310 can be selected to have a higher adhesivestrength between carrier film 310 and wafer 100 compared to the adhesivestrength between carrier tape 30 and wafer 100. In one embodiment, thedifference in adhesive strengths can be selected to better maintain thedie in place while carrier tape 30 is subsequently removed after layer281 is singulated or separated. Carrier tape 30 is selected to have anadhesive strength sufficient to remove material from the singulationlines without pulling the die away from carrier film 310 or damaging theremaining layer 281 material on the individual die.

In optional step 1301, a localized pressure is applied to at least oneside of wafer 100 to initiate cracks, crack lines, or separation linesin layer 281 within the singulation lines. In one embodiment, stylus 611can be used. In another embodiment, a pressurized liquid or gas can beused. In one embodiment, the localized pressure can be applied the frontside of wafer 100. In another embodiment, the localized pressure can beapplied to the backside of wafer 100. In a further embodiment, thelocalized pressure can be applied to both sides of wafer 100.

In step 1302, carrier tape 30 can be optionally exposed to a UV lightsource and then removed wafer 100. In one embodiment, the removal ofcarrier tape 30 during step 1302 removes material from singulation lines13, 15, 17, and 19, which is facilitated by the differences in adhesivestrengths between carrier film 310 and carrier tape 30. In oneembodiment, the removal of the material can be facilitated withouthaving to stretch the carrier tape or use the stylus to separate theback metal or back layer, although removal of the metal will requireless adhesive force if separated by the stylus prior to the removal ofcarrier tape 30.

In step 1303, a new carrier tape can be applied to the backside of wafer100, and then carrier film 310 can be removed from the front side ofwafer 100 in step 1304. Wafer 100 can then be subjected to furtherprocessing.

It was found that the present embodiments produce improved resultscompared to methods using carrier tapes on one side of the wafer only.In accordance with the present embodiment, carrier tape layers areplaced on both sides of the wafer during the singulation of the backsidematerial. The present embodiment improves the quality of the singulatedbackside material and reduces yield loss due to singulation linespropagating into die active areas.

From all of the foregoing, one skilled in the art can determine that,according to one embodiment, a method of singulating a wafer (forexample, elements 10, 100) comprises providing a wafer having aplurality of die (for example, elements 12, 14, 16, 18) formed on thewafer and separated from each other by spaces, wherein the wafer hasfirst and second opposing major surfaces (for example, elements 21, 22),and wherein a layer of material (for example, elements 28, 281) isformed along the second major surface. The method includes placing thewafer onto a first carrier substrate (for example, element 30), whereinthe layer of material is adjacent the first carrier substrate. Themethod includes singulating the wafer through the spaces to formsingulation lines (for example, elements 13, 15, 17, 19), whereinsingulating includes stopping in proximity to the layer of material. Themethod includes applying a localized pressure (for example, element 61,71, 710, 81) to at least one of the first major surface or the secondmajor surface to separate the layer of material in the singulationlines.

From all of the foregoing, one skilled in the art can determine that,according to another embodiment, a method of singulating die from awafer (for example, elements 10, 100) comprises providing a wafer havinga plurality of die (for example, elements 12, 14, 16, 18) formed on thewafer and separated from each other by spaces, wherein the wafer hasfirst and second opposing major surfaces (for example, elements 21, 22)and wherein a layer of material (for example, elements 28, 281) isformed along the second major surface. The method includes placing thewafer onto a first carrier substrate (for example, element 30), whereinthe layer of material is adjacent the first carrier substrate;singulating the wafer through the spaces to form singulation lines (forexample, elements 13, 15, 17, 19), wherein the singulation linesterminate before penetrating completely through the layer of material.The method includes placing the wafer onto to a second carrier substrate(for example, element 310), wherein the layer of material is opposite tothe second carrier substrate. The method includes moving a mechanicaldevice along the second carrier substrate to separate the layer ofmaterial in the singulation lines.

In one embodiment of the foregoing method, placing the wafer onto thefirst carrier substrate can include placing the wafer onto a firstcarrier tape, and placing the wafer onto the second carrier substratecan include placing the wafer onto a second carrier tape. In anotherembodiment, moving the mechanical device can include moving at least onestylus. In an additional embodiment, providing the wafer can includeproviding a semiconductor wafer having a wafer backside coating layeroverlying the second major surface. In a further embodiment, singulatingthe wafer can include plasma etching the wafer.

From all of the foregoing, one skilled in the art can determine that,according to an additional embodiment, a method of singulating asubstrate (for example, elements 10, 100) comprises providing asubstrate having a plurality of die (for example, elements 12, 14, 16,18) formed on the substrate and separated from each other by spaces,wherein the substrate has first and second opposing major surfaces (forexample, elements 21, 22), and wherein a layer of material (for example,elements 28, 281) is formed overlying the second major surface. Themethod includes placing a carrier tape (for example, element 30) ontothe layer of material. The method includes plasma etching the substratethrough the spaces to form singulation lines (for example, elements 13,15, 17, 19), wherein the singulation lines terminate in proximity to thelayer of material. The method includes placing a carrier film (forexample, element 310) onto the substrate opposite to the layer ofmaterial. The method includes applying a localized pressure to the firstmajor surface using a mechanical device to separate the layer ofmaterial.

In one embodiment of the foregoing method, applying a localized pressurecan include applying a localized pressure with at least one stylus. Inanother embodiment providing the substrate includes providing asemiconductor wafer having a wafer backside coating layer formedoverlying the second major surface.

From all of the foregoing, one skilled in the art can determine that,according to further embodiment, a method of forming an electronicdevice comprises providing a wafer (for example, elements 10, 100)having a plurality of die (for example, elements 12, 14, 16, 18) formedon the wafer and separated from each other by spaces, wherein the waferhas first and second opposing major surfaces (for example, elements 21,22), and wherein a layer of material (for example, elements 28, 281) isformed along the second major surface, and wherein the layer of materialis placed on a first carrier substrate. The method includes singulatingthe wafer through the spaces to form singulation lines (for example,elements 13, 15, 17, 19). The method includes placing the wafer onto asecond carrier substrate (for example, element 310), wherein the layerof material is opposite to the second carrier substrate. The methodincludes moving a mechanical device along one of the first or secondcarrier substrates to separate the layer of material in the singulationlines.

In one embodiment of the foregoing method, placing the wafer onto thefirst carrier substrate can include placing the wafer onto a firstcarrier tape, and placing the wafer onto the second carrier substratecan include placing the wafer onto a second carrier tape. In anotherembodiment, moving the mechanical device can include moving themechanical device with both the first carrier substrate and the secondcarrier substrate attached to the wafer. In an additional embodiment,moving the mechanical device can include moving at least one carriersubstrate. In a further embodiment, moving the mechanical device caninclude moving at least one stylus along the second carrier substrate.In a still further embodiment, moving the mechanical device can includemoving the mechanical device while the first carrier tape is placedagainst a compressive layer. In another embodiment, placing the waferonto the second carrier substrate can include placing the wafer onto thesecond carrier substrate, wherein the second carrier substrate has ahigher adhesive strength than the first carrier substrate. In anadditional embodiment, one or more of the foregoing methods can furtherinclude removing the first carrier substrate after moving the mechanicaldevice, wherein removing the first carrier substrate removes portions ofthe layer of material in the singulation lines. In one embodiment,removing the first carrier substrate can include removing the firstcarrier substrate without stretching either the first or the secondcarrier tapes before the first carrier tape is removed.

From all of the foregoing, one skilled in the art can determine that,according to a still further embodiment, an apparatus for separating die(for example, elements 12, 14, 16, 18) from a wafer (for example,elements 10, 100) comprises a structure for holding the wafer on acarrier substrate, wherein the semiconductor wafer has a plurality ofsingulation lines that terminate proximate to a layer of material on thewafer; and a structure for applying a localized pressure (for example,elements 61, 71, 81) to the wafer through the carrier substrate.

In one embodiment of the foregoing apparatus the semiconductor wafer hasa plurality of singulation lines etched through the semiconductor wafer.In another embodiment, the singulation lines are plasma etched throughthe semiconductor wafer. In an additional embodiment, the structure forapplying the localized pressure can be configured to move in relation tothe wafer. In a further embodiment, the structure for applying thelocalized pressure can be configured to rotate. In a still furtherembodiment, the structure for applying the localized pressure comprisesmore than one stylus. In one embodiment, the structure for holding caninclude a compressive layer (for example, element 733). In anotherembodiment, the compressive layer comprises a pressurized membranestructure.

From all of the foregoing, one skilled in the art can determine that,according to another embodiment, a method of singulating a substratecomprises providing a substrate (for example, elements 10, 100) having aplurality of die (for example, elements 12, 14, 16, 18) formed on thesubstrate and separated from each other by spaces, wherein the substratehas first and second opposing major surfaces (for example, elements 21,22), and wherein a layer of material (for example, elements 28, 281) isformed overlying the second major surface. The method includes placing acarrier tape (for example, element 30) onto the layer of material. Themethod includes plasma etching the substrate through the spaces to formsingulation lines (for example, elements 13, 15, 17, 19), wherein thesingulation lines terminate in proximity to the layer of material. Themethod includes applying a localized pressure to the second majorsurface using a mechanical device (for example, elements 61, 71, 81) toseparate the layer of material.

From all of the foregoing, one skilled in the art can determine that,according to an additional embodiment, a method of singulating asubstrate comprises providing a substrate (for example, elements 10,100) having a plurality of die (for example, elements 12, 14, 16, 18)formed on the substrate and separated from each other by spaces, whereinthe substrate has first and second opposing major surfaces (for example,elements 21, 22), and wherein a layer of material (for example, elements28, 281) is formed overlying the second major surface. The methodincludes placing a first carrier tape (for example, element 30) onto thelayer of material. The method includes plasma etching the substratethrough the spaces to form singulation lines (for example, elements 13,15, 17, 19), wherein the singulation lines terminate in proximity to thelayer of material. The method includes placing a second carrier tape(for example, element 310) onto the substrate opposite to the layer ofmaterial; and removing the first carrier tape to separate the layer ofmaterial in singulation lines.

From all of the foregoing, one skilled in the art can determine that,according to further embodiment, a method of singulating a substratecomprises providing a substrate (for example, elements 10, 100) having aplurality of die (for example, elements 12, 14, 16, 18) formed on thesubstrate and separated from each other by spaces, wherein the substratehas first and second opposing major surfaces (for example, elements 21,22), and wherein a layer of material (for example, elements 28, 281) isformed overlying the second major surface. The method includes placing afirst carrier tape (for example, element 30) onto the layer of material.The method includes plasma etching the substrate through the spaces toform singulation lines (for example, elements 13, 15, 17, 19), whereinthe singulation lines terminate in proximity to the layer of material.The method includes placing a second carrier tape (for example, element310) onto the substrate opposite to the layer of material. The methodincludes applying a localized pressure to one major surface of thesubstrate using a mechanical device (for example, 61, 71, 81) toseparate the layer of material in the singulation lines while substrateis attached to both the first and second carrier tapes.

From all of the foregoing, one skilled in the art can determine that,according to a still further embodiment, a method of singulating asubstrate comprises providing a substrate (for example, elements 10,100) having a plurality of die (for example, elements 12, 14, 16, 18)formed on the substrate and separated from each other by spaces, whereinthe substrate has first and second opposing major surfaces (for example,elements 21, 22), and wherein a layer of material (for example, elements28, 281) is formed overlying the second major surface. The methodincludes placing a first carrier tape (for example, element 30) onto thelayer of material. The method includes plasma etching the substratethrough the spaces to form singulation lines, wherein the singulationlines terminate in proximity to the layer of material. The methodincludes placing a second carrier tape (for example, element 310) ontothe substrate opposite to the layer of material. The method includesremoving the first carrier tape to separate the layer of material insingulation lines.

In view of all of the above, it is evident that a novel method andapparatus are disclosed. Included, among other features, is placing asubstrate having a layer of material on a major surface of the substrateonto a carrier tape, and forming singulation lines through the substrateto expose portions of the layer of material within the singulationlines. A second carrier tape is applied to the front side of thesubstrate, and a mechanical device that provides a localized pressure tothe front side of the substrate is used to separate the layer ofmaterial from the back side of the substrate while the substrate hascarrier tape layers on both sides. The method provides, among otherthings, an efficient, reliable, and cost effective process forsingulating substrates that include back layers, such as thicker backmetal layers or WBC layers.

While the subject matter of the invention is described with specificpreferred embodiments and example embodiments, the foregoing drawingsand descriptions thereof depict only typical embodiments of the subjectmatter, and are not therefore to be considered limiting of its scope. Itis evident that many alternatives and variations will be apparent tothose skilled in the art. For example, other forms of removable supportmaterials can be used instead of carrier tapes.

As the claims hereinafter reflect, inventive aspects may lie in lessthan all features of a single foregoing disclosed embodiment. Thus, thehereinafter expressed claims are hereby expressly incorporated into thisDetailed Description of the Drawings, with each claim standing on itsown as a separate embodiment of the invention. Furthermore, while someembodiments described herein include some but not other featuresincluded in other embodiments, combinations of features of differentembodiments are meant to be within the scope of the invention and meantto form different embodiments as would be understood by those skilled inthe art.

What is claimed is:
 1. A method of singulating die from a wafercomprising: providing a wafer having a plurality of die formed as partof the wafer and separated from each other by spaces, wherein the waferhas first and second opposing major surfaces, and wherein a layer ofmaterial is disposed along the second major surface; placing the waferonto a first carrier substrate, wherein the layer of material isadjacent the first carrier substrate; singulating the wafer through thespaces to form singulation lines while the wafer is coupled to the firstcarrier substrate, wherein the singulation lines terminate beforepenetrating completely through the layer of material; placing asubstrate adjacent the first major surface, wherein the wafer isinterposed between the substrate and the first carrier substrate; andmoving a mechanical device along the substrate to separate the layer ofmaterial in the singulation lines.
 2. The method of claim 1 furthercomprising applying heat to at least the first carrier substrate.
 3. Themethod of claim 1 further comprising stretching the first carriersubstrate during the step of moving the mechanical device.
 4. The methodof claim 1, wherein moving the mechanical device comprises moving atleast one stylus.
 5. The method of claim 1, wherein singulating thewafer comprises plasma etching the wafer.
 6. A method of singulating awafer comprising: providing a wafer having a plurality of die formed aspart of the wafer and separated from each other by spaces, wherein thewafer has first and second opposing major surfaces, and wherein a layerof material is disposed along the second major surface; placing thewafer onto a carrier tape, wherein the layer of material is adjacent thecarrier tape; singulating the wafer through the spaces to formsingulation lines, wherein singulating includes stopping in proximity tothe layer of material; placing a substrate adjacent the first majorsurface of the wafer such that the wafer is interposed between thecarrier tape and the substrate; and moving a mechanical device in adirection generally parallel to and adjoining one of the carrier tape orthe substrate to separate the layer of material in the singulation line.7. The method of claim 6 further comprising: applying heat to at leastthe carrier tape; and stretching the carrier tape, wherein: singulatingcomprises plasma etch singulating with the wafer coupled to the carriertape; and moving the mechanical device comprises applying a compressiveforce generally perpendicular to the first major surface and the secondmajor surface.
 8. The method of claim 6 further comprising stretchingthe carrier tape while moving the mechanical device, wherein moving themechanical device comprises applying a compressive force generallyperpendicular to the substrate.
 9. The method of claim 6, whereinplacing the substrate comprises placing a second carrier tape.
 10. Themethod of claim 1, wherein placing the substrate comprises placing asecond carrier tape.
 11. A method of singulating a wafer comprising:providing a wafer having first and second opposing major surfaces, aplurality of die formed adjacent the first major surface, a layer ofmaterial along the second major surface, the plurality of die separatedby singulation lines that terminate in proximity to the layer ofmaterial, and a first carrier substrate adjoining the layer of material,wherein the layer of material comprises a conductive material; placing asubstrate adjacent the first major surface of the wafer such that thewafer is interposed between the first carrier substrate and thesubstrate; and moving a mechanical device in a direction generallyparallel to and adjoining one of the first carrier substrate or thesubstrate to separate the layer of material in the singulation lines.12. The method of claim 11, wherein providing the wafer comprises:plasma etching the wafer through spaces between the plurality of die toform the singulation lines.
 13. The method of claim 11, wherein movingthe mechanical device comprises: placing the mechanical device inphysical contact with the substrate; and moving the mechanical deviceagainst the substrate.
 14. The method of claim 13 further comprisingplacing the first carrier substrate into physical contact with acompressive layer during the moving step.
 15. A method of singulating awafer comprising: providing a wafer having first and second opposingmajor surfaces, a plurality of die formed adjacent the first majorsurface, a layer of material along the second major surface, theplurality of die separated by singulation lines that terminate inproximity to the layer of material, and a first carrier substrateadjoining the layer of material; placing a substrate adjacent the firstmajor surface of the wafer such that the wafer is interposed between thefirst carrier substrate and the substrate; moving a mechanical device ina direction generally parallel to and adjoining one of the first carriersubstrate or the substrate to separate the layer of material in thesingulation lines; and placing the first carrier substrate into physicalcontact with a compressive layer during the moving step.
 16. The methodof claim 11, wherein placing the substrate comprises placing a carriertape.
 17. The method of claim 11 further comprising applying heat to atleast the first carrier substrate during at least a portion of the stepof moving the mechanical device.
 18. The method of claim 11 furthercomprising stretching the first carrier substrate during at least aportion of the step of moving the mechanical device.
 19. The method ofclaim 11, wherein moving the mechanical device comprises moving at leastone stylus.
 20. The method of claim 11, wherein moving the mechanicaldevice comprises applying a compressive force generally perpendicular tothe substrate.